Many electronic assemblies contain components that are sensitive to radio frequency (RF) signals or that emit RF signals. RF interference, also known as electromagnetic interference (EMI), is an extremely important issue in determining the functionality and proper performance and conformance to regulations of electrical assemblies. Many components in an electronic assembly may emit RF signals and numerous regulations exist that limit the amount or extent of RF emission that may occur from an electrical article. In addition, many devices within the electronic assembly are sensitive to RF signals. In order to comply with regulations and to protect sensitive components from RF interference, RF shields are often placed around the critical components. A radio-frequency (RF) shield is a shield that prevents radiofrequency electromagnetic radiation from entering or leaving or passing through the shield. The shields may be as simple as a single metal housing enclosing the entire electrical assembly or as complex as custommade miniature housings or enclosures for each individual electronic component.
Often, a component must be shielded from electrical interference emanating from inside a printed circuit board itself. In addition to enclosing the component with a covering or a shield, a shield of some sort must be provided underneath the component, that is, between the component and the printed circuit board to shield it from interferences arising from the boards. This type of shielding is typically provided by placing a piece of metal foil, such as copper foil, between the component and the printed circuit board and attaching at least one portion of the metal foil to part of the circuitry on the printed circuit board, typically the ground. If necessary, the metal foil may be insulated by a dielectric or insulating material to avoid shorting between the shield and the printed circuit board or the shield and the component. These types of metal foil shields are typically hand soldered to the printed circuit board. This operation typically occurs after reflow assembly and requires special locating and holding fixtures. Any manual operation requires extra labor, therefore, extra cost is added to the end product. In addition, manual assemblies allow defects to be introduced into the final assembly. Because these soldering operations are difficult to control and can occasionally generate a great deal of heat that damages the printed circuit board and surrounding sensitive components. In addition, any design changes in the component layout will require new shapes or tooling for the metal foil shields. Clearly, the need to employ unique components, extra tooling and fixtures, the high cost of manual operation, generation of assembly defects, and potential damage to the circuitry and surrounding components are all disadvantages of the conventional method of shielding. A shielding method which would eliminate these types of problems would be highly desirable in the printed circuit board industry.